58 WILD AND CULTIVATED COTTONS 



Nectar- Numerous writers have discussed these foliar glands. Pro- 



Eunds" 18 fes80r William Trelease (' Nectar, Its Nature, Occurrence, and 

 Uses,' published in J. Henry Comstock's ' Report on Cotton Insects,' 

 p. 327) points out that the glands of the leaf begin to secrete when 

 the seedling has about four leaves expanded. He also states that 

 the nectar is most copiously produced during night. Mr. W. Edwin 

 Safford (' Useful Plants of Guam,' published in ' Contrib. United 

 States Nat. Herb.' ix. p. 67) gives a much enlarged microscopic 

 section, showing their formation. Mr, Q. F. Cook ' (Weevil-Resisting 

 Adaptations, Cotton Plant,' ' United States Dept. Agri. Bull.,' No. 88 of 

 1906, p. 30) maintains that they have been brought into existence 

 in order to induce friendly insects to visit all parts of the plant. 

 [Cf. Darwin, ' Cross and Self Fertilisation,' pp. 403-4 ; Delpino, 

 ' Rapporti tra insetti e tra nettari estranuziali,' p. 63 ; Cook, 

 'United States Dept. Agri. Rep.' No. 78; also ' Bull. Entom.,' 

 No. 49 (1904)]. 



Extra- 3. Extra-floral glands. There may be said to be two sets of 



glands of this nature (a) three placed on the apex of the peduncle 

 embraced or surrounded by the auriculate bases of the bracteoles, and 

 (b) three additional glands placed on the base of the calyx-tube, within 

 and alternate with the bracteoles. These are all more or less circular 

 glands, and usually of a bright yellow or red colour. It will be seen 

 that in the classification of the genus Gossypium, adopted by me, I have 

 put some value on the presence or absence of these glands. But as 

 observed, in connection with the foliar nectaries, the constancy of the 

 extra-floral glands can alone be depended on with the non-cultivated 

 species. They secrete a large amount of sweet fluid, which, as Pro- 

 fessor Trelease (I.e.) and before him Glover (' Agri. Rept.,' 1855, 

 p. 234) have pointed out, forms an attractive food for certain insect 

 visitants. The former author says these glands are not formed on 

 the first few flowers, but that subsequently all possess the outer set, 

 ' though it is not till the cotton has been blooming about a month 

 that the inner set appear.' The evening before the flower unfolds, 

 its glands begin to visibly secrete the nectar. 



Stipular Their Morphology. With regard to the morphology of these glands 



1 8 ' it has been commonly supposed that they represent two abortive 

 whorls of bracts. In Gossypium Stocksii a pair of minute glands occur 

 on either side of the thickened claw (Plate No. 6, ff. 4, 5), and thus are 

 clearly stipular in origin. Mr. Cook has pointed out that the extra- 

 floral glands, in the Guatemalan cotton, are unusually large, the inner 



